x86/PCI: remove 64-bit division

The roundup() caused a build error (undefined reference to `__udivdi3').
We're aligning to power-of-two boundaries, so it's simpler to just use
ALIGN() anyway, which avoids the division.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>